Model from Sketchup to Blender
I just did an experiment:

Created a 2 meter cube in Sketchup Make 2017.

Exported as a.dae file.

Imported to Blender.





After Applying the scale in Object mode the dimensions were correct.





I have no idea why the imported cube was scaled to 0.025 but maybe something similar is happening with your imports.

If the scale is not 1.0 in the X, Y and or Z then try applying Scale.

In Object mode: with object selected, Ctrl + A  to open Apply menu.



If you do some maths on the edge lengths of 78.74 shown in edit mode of the "2x2x2m cube" (before applying Scale) (see second image in previous post) you will notice:

78.74 / 2 = 39.37   (Divide by 2 to find length for 1 meter)

39.37 x 0.025 = 0.98125    ( multiplied by 0.025 because that is the scale showing in Object mode.  See the first image in my previous post. This is very close to 1 meter.

The Scale of 0.025 reminded me of the number you get when converting inches to metric. 1 inch = 0.0254 meters.

I know almost nothing about collada files but do know you can open them in a text editor and have a look inside.

This is what the first few lines of the 2 meter cube exported from Sketchup look like. 



And this is the first few lines of the collada.dae file of a 2 meter cube created and exported from Blender as a Collada.dae file:



Perhaps you need to find some setting in the Sketchup exporter setup to correct this?

Or maybe you could try editing the unit line in the Collada file so that it reads the same as the the Collada file exported from Blender.



No I am not a sketchup user, I just had it on my computer because a a while ago i wanted to see how it works.



I noticed that in the Blender Collada Import menu there is an Inport Units option.